Multi-Scale Applications of U.S. EPA s Third-Generation Air Quality Modeling System (Models-3/CMAQ) Carey Jang, Pat Dolwick, Norm Possiel, Brian Timin, Joe Tikvart U.S. EPA Office of Air Quality Planning and Standards (OAQPS) Research Triangle Park, NC, U.S.A.
OUTLINE Models-3/CMAQ system One-Atmosphere perspective Multi-Scale Applications of Models-3/CMAQ Western U.S. Application Annual Nationwide U.S. Application Eastern U.S. Application Hemispheric/Continental Modeling Initiative
Open-Access Community-Based Models : User-friendly, Modular, Common modeling framework for scientists and policy-makers. Advanced Computer Technologies : High performance hardware and software technologies (Cross-platform, GUI, distributed computing, visualization tools, etc.). One-Atmosphere Modeling : Multi-pollutant (Ozone, PM, visibility, acid deposition, air toxics, etc.), Multi-scale.
Regulating Air Pollution: One-Atmosphere Approach (Cars, trucks, airplanes, boats, etc.) Mobile Sources (Power plants, factories, refineries/chemical plants, etc.) (Homes, small business, farming equipment, etc.) NOx, VOC, Toxics Industrial Sources Chemistry NOx, VOC, SOx, Toxics Area Sources NOx, VOC, Toxics Meteorology Ozone PM Acid Rain Visibility Air Toxics Atmospheric Deposition
NOx-Related Air Quality Issues (NO3 -, NH4 + ) PM (NOx + VOC + hv) --> Ozone NOx Acid Rain (NO3 - deposition) Visibility (Fine PM) Water Quality (Nitrogen deposition, Lake Acidification)
SOx-Related Air Quality Issues (SO4 2-, NH4 + ) PM (Fine PM) Visibility SOx Acid Rain (SO4 2- deposition) Water Quality (Lake acidification, Toxics deposition)
. OH role in pollutants formation : One-Atmosphere VOC + OH ---> Orgainic PM PM2.5 2.5 SOx [or NOx] + NH3 + OH ---> (NH4)2SO4 [or NH4NO3] Fine PM (Nitrate, Sulfate, Organic PM) Visibility. OH Ozone NOx + VOC + OH + hv ---> O3 Water Quality NOx + SOx + OH (Lake Acidification, Eutrophication) Air Toxics Acid Rain OH <---> Air Toxics (POPs, Hg(II), etc.) SO2 + OH ---> H2SO4 NO2 + OH ---> HNO3
Example of One-Atmosphere Modeling Impact of 50 % NOx Emission Reduction on PM 2.5
Impact of 50% NOx emission reduction Nitrate PM decrease Sulfate PM decrease
Impact of 50% NOx emission reduction O3 decrease HOx decrease
Models-3/CMAQ Applications at OAQPS Purpose: To evaluate Models-3/CMAQ feasibility as a regulatory tool Western U.S. Application New domain, episodic O3O Annual Nationwide U.S. Application Annual PM & visibility Eastern U.S. Application Urban & SIP applications Hemispheric/continental Modeling Initiative Linkage of climate change and air pollution
Western U.S. Application Objectives : New M3/CMAQ Domain New Episode (July 1996) Model Setup : Episodic O 3 modeling Meteorology : MM5 Emissions : Tier-2 2 regridded 36km/12km, 12 layers Compare against observations and UAM-V 177 153
Annual Nationwide U.S. Application Objectives : Annual CMAQ Run Nationwide CMAQ Domain Model Setup : Annual PM and O3 O (1996) 36-km, 8 vertical layers Meteorology : MM5 Emissions Processing: SMOKE Model Evaluation: Compared against observed data (IMPROVE & CASTNET) & REMSAD
Models-3/CMAQ Simulation: Annual Average PM 2.5 Sulfate PM Nitrate PM Organic PM
O3 (July Max) Visibility (1996 avg.)
National 1996 CMAQ Modeling (January average) Sulfur Wet Deposition Nitrogen Wet Deposition
CMAQ Sensitivity Studies CB4 vs.. RADM2 Is RADM2 a better mechanism than CB4 for PM modeling? Run CMAQ w/ both CB4 and RADM2 for January and July, 1996 NH3 sensitivity Are NH3 emissions the culprit of nitrate PM over- prediction? Run CMAQ w/ 50% reduction of NH3 emissions for January and July, 1996 Boundary conditions sensitivity Run CMAQ w/ 10 ppb O3 increase along the western boundary for January and July, 1996
Original CB4 RADM2
4 Orig. CB4 RADM2 Fixed CB4
3 3
CMAQ Sensitivity : Boundary Conditions Effect of a 10 ppb ozone increase along the western boundary
Eastern U.S. Application Objectives : SIP and urban applications Emission growth & control Nested MM5 runs Features : O3 and PM, July 95 OTAG-like 36/12-km domain, nested with 4-km 4 (NE, LM, AT, TX) SMOKE : Emissions processing
Climate Change/Air Pollution Modeling Initiative Proposal : Global and Regional Modeling of Ozone and PM Goal : Establish linkages between climate change and air pollution
Climate Change/Air Pollution Modeling Initiative Background : O3 and PM are not only key air pollutants, but also major climateforcing substances; Reduction of non-co2 substances (e.g., O3 and PM, especially black carbon) could be a viable alternative to CO2 reduction to curb global warming. A key strategy suggested was to focus on air pollution to benefit regional and local air quality and global climate simultaneously (Hansen et al., PNAS, 2000); Black carbon could be the second largest heating component after CO2 contributing to global warming; Control of fossil-fuel black carbon could be the most effective method of slowing glabal warming (Jacobson, Nature, 2001);
Climate Change/Air Pollution Modeling Initiative O3 (0.3+0.1) Black (0.8) Carbon (Hansen et al., PNAS2001)
Climate Change/Air Pollution Modeling Initiative Background (continued): There is also mounting evidence that criteria pollutants originating from some developing countries, especially those in Asia such as China and India, could impact U.S. domestic air quality as well as contribute to the global background of climate-forcing substances. This intercontinental transport issue is expected to worsen with the rapid growth in emissions in these regions. For example, recent modeling studies showed that by 2020 Asian emissions could contribute as much as 2 ~ 6 ppb of O 3 in the western U.S., offsetting the Clean Air Act efforts up to 25% in that region (Jacob et al., Geophys. Res. Letts., 1999) and increase global mean O 3 level up to 10% (Collins et al., Atmos. Env., 2000); Asian and Sahara dust could contribute a significant amount of PM in the western and southeastern U.S. (Husar, http://capita.wustl.edu/capita/).!
Climate Change/Air Pollution Modeling Initiative Models-3/CMAQ Run Example Ozone (ppm) 1998 April 11: 1200 UTC (Byun and Uno, 2000)
Climate Change/Air Pollution Modeling Initiative Objectives : To evaluate available approaches for establishing the linkages between air pollution and climate change and enhancing modeling capacity within EPA to address these linkage issues. To explore the impacts of intercontinental transport of O3 and PM as well as their implications for domestic and regional air quality and global climate change To design integrated emissions control strategies to benefit global climate and regional and local air quality simultaneously
Climate Change/Air Pollution Modeling Initiative Work Plan : Phase I : Short-Term (~6 months) Establish a better scientific foundation in linking climate change and air pollution by leveraging current studies 1. Global Modeling of O3 and PM 2. Global Radiative Forcing of Aerosols 3. Emission Inventories for Climate-Forcing Pollutants Develop a conceptual model and modeling protocol under the guidance of an expert advisory panel
Climate Change/Air Pollution Modeling Initiative Work Plan : Phase II : Long-Term (1 ½~2 years) Based on Phase I effort, a series of modeling efforts that will be conducted to address the linkages between air pollution and climate change. These efforts may include: Enhancement of modeling capability and emission inventories to better represent the linkages to global air quality and climate. Development of nesting capability between global chemistry/climate models and regional air quality models. Simulation of hemispheric or regional air quality under a variety of scenarios about future global and regional emissions and air quality. Evaluation of global and regional air quality models using a diverse set of observational data sets, including data from satellites, surface networks, intensive field studies, etc. Assessment of the potential radiative forcing and climate benefits resulting from planned and alternative non-co2 control strategies